Community assembly patterns of parids along an elevational gradient in western China

Eight species of parids commonly occur in the mountains of northern Sichuan Province, People's Republic of China. They represent four monophyletic gro ups regarded by some authorities as genera, but more traditionally as subge nera of the large genus Parus. To test the competition-based hypothesis tha t less closely related species are more likely to co-occur, we used specime ns and observations obtained in October 1989 and May 1991 to delineate the morphology, elevational range, and habitat associations of each species in this rich assemblage. A morphometric cluster analysis did not support the a ssumption that phylogenetic similarity predicts morphological and hence eco logical similarity. Up to five species commonly co-occurred in mixed flocks , as in Europe (where five subgenera are represented), but a randomization test showed that community assembly was random with respect to subgenus. On the other hand, for the entire data set (P = 0.05) and during spring (P = 0.07), species in the same morphometric cluster were less Likely to co-occu r than were species with dissimilar morphology. It appears, therefore, that competition between species of similar morphology may play (or have played ) some role in structuring assemblages of parids during the breeding season in this area. For this reason, more detailed studies of the parid assembla ge in this area are recommended.